1. Field of the Invention
The present invention relates generally to oscillators, and in particular, to a method, apparatus, and article of manufacture for utilizing stable, low-noise, self-sustaining active oscillators operating at ultra-high frequency, based upon vibrating nanoelectromechanical resonators (NEMS resonators).
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by reference numbers enclosed in brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Self-sustaining oscillators possess the unique property of spontaneously generating periodically occurring events and sustaining these oscillations by extracting energy from non-periodic sources. They exist in nature in many fields ranging from biological circadian rhythms [1] to fluids flows [2] and dynamic systems [3]. They also find important applications in human-enabled systems such as navigation and communication [4], sensors and transducers [5], clocks and timekeeping [6], where the technological progresses have mainly been driven to attain ultrafast (wide bandwidth) operation, high-precision, low-power and ultrahigh integration densities. Over the years it is proven that stable oscillators based on mechanical resonators made from high-quality crystals [7] are excellent solutions for the aforementioned applications. A recent thrust seeks to develop oscillators based on micro- and nanoscale vibrating mechanical devices [8].
Despite the great impetus and efforts in miniaturizing mechanical resonators, following that of the electronics for some 40 years [9], there have been formidable challenges for realizing self-sustaining oscillators with crystalline mechanical devices at the micro and nanoscale. While the operating frequencies have been remarkably scaled up into the regimes well beyond those of conventional crystal oscillators, by exploiting advanced nanofabrication techniques to keep shrinking the dimensions of these micro and nanodevices [10, 11], their electromechanical characteristics (usually described by equivalent circuit models) become increasingly incongruous with readout electronics, and the devices response signal levels decrease drastically [10, 11, 12]. For example, hitherto the state-of-the-art microelectromechanical system (MEMS) oscillators have only been realized at frequencies as high as ˜60 MHz [12]. Meanwhile, recently reported nanoelectromechanical system (NEMS) resonators made from both lithographically-patterned nanobeams [10, 11] and chemically-synthesized nanowires [13] and nanotubes [14], although operatable at very-high and ultra-high frequencies (VHF and UHF), all are passive resonators.
Accordingly, what is needed is a high frequency, self-sustaining, active oscillator with practical complexity and functionality.